Technical Field
The present invention relates, in general, to a system and method for detecting ambiguities in satellite signals for vessel positioning and, more particularly, to a system and method for detecting ambiguities in satellite signals for vessel positioning, which can detect ambiguities in satellite signals used to measure the position of a vessel.
Background Art
Periodically acquiring the position of a vessel for safe navigation of the vessel has been a continuous matter of interest for the development of new technology since the initiation of navigation on the sea. Recently, a Global Navigation Satellite System (GNSS) position acquisition system for acquiring the position of a user receiver based on the principle of triangulation by measuring the position of a satellite rotating around the earth and a distance from the satellite to the user receiver has been utilized as the most important vessel position acquisition means.
FIG. 1 is a block diagram showing a conventional system for determining a marine vessel position and providing an information service, and FIG. 2 is an internal plan view showing a conventional vessel position detection system.
For example, Korean Patent Application No. 10-1994-028555 discloses a system for determining the precise current position of each vessel on the sea and providing various types of information necessary for the vessel by utilizing a Global Positioning System (GPS) receiver and a Trunked Radio System (TRS), and a processing method of the system. Further, Korean Patent Application No. 10-2006-0045403 discloses a system and method for detecting the position of a vessel, which are capable of utilizing both a distance and an azimuth angle between a berth and a vessel, measured by a laser range finder 202 and then accurately providing the position and the sailing distance of the vessel.
Meanwhile, the acquisition of vessel position using a GNSS has been used in almost all vessels owing to an advantage that vessel positions may be acquired from the overall region of the earth regardless of weather conditions. However, such technology uses radio waves, and thus various types of technologies for acquiring information above a predetermined level required for vessels have been developed from the standpoint of precision and integrity. The elimination of ambiguities (plausibility) in positioning signals, which may occur because of artificial blocking of GNSS signals attributable to jamming signals that frequently and recently occur and errors in the positioning of a user receiver that occurs due to a failure in a satellite system, has been emphasized as an important issue.
The ambiguities in vessel position acquired by a user receiver using satellite radio waves was understood to be a concept included in the precision of vessel position in the past. However, it is assumed that the precision of positioning results caused by various error factors such as an inherent error in a GNSS system itself, an error caused by a delay on an ionized layer or an ionosphere at a distance by which radio waves reach a user receiver, an error in the user receiver, and a signal tracking error caused by multipath effects attributable to the surrounding environment of a user and other radio interference is represented by a probability that, when comparing calculated positioning information with true values of positioning information, the calculated positioning information will fall within a predetermined range. In this case, the precision of positioning information that can be guaranteed by the user receiver is provided based on the assumption of generally expected errors. Accordingly, a problem arises in that when an artificial error is applied thereto, the precision of positioning information cannot be guaranteed.
In this way, in a situation in which precision is obstructed, if the vessel position of a user corresponds to positioning information obtained when a vessel is rolled in several directions while deviating from a predetermined range, the user may definitely recognize the inaccuracy of information. However, when the vessel position corresponds to positioning information having a continuous error in a certain direction, it may be difficult for a user to promptly recognize that determined position information is inaccurate positioning information, and a problem arises in that ambiguities may be contained in such inaccuracy.